Pneumatic tire having an innerliner comprised of butyl rubber and dispersion of ethylene vinyl alcohol polymer

Abstract: The present invention relates to a pneumatic rubber tire having an integral innerliner of a sulfur cured rubber composition. The innerliner rubber composition is comprised of at least one elastomer selected from bromobutyl rubber and chlorobutyl rubber which also contains a dispersion therein of ethylene vinyl alcohol polymer. (end of abstract)

Pneumatic tire having an innerliner comprised of butyl rubber and dispersion of ethylene vinyl alcohol polymer description/claims

Brief Patent Description

Full Patent Description

Patent Application Claims

FIELD OF THE INVENTION

The present invention relates to a pneumatic rubber tire having an integral innerliner of a sulfur cured rubber composition. The innerliner rubber composition is comprised of at least one elastomer selected from butyl rubber, bromobutyl rubber and chlorobutyl rubber which also contains a dispersion therein of ethylene vinyl alcohol polymer.

BACKGROUND OF THE INVENTION

The inner surface of a pneumatic tire is typically comprised of an elastomeric composition designed to prevent or retard the permeation of air and moisture into the carcass from the tire\'s inner air chamber. It is often referred to as an innerliner. Rubbers, such as halobutyl rubber and blends of butyl and halobutyl rubber, which are relatively impermeable to air are often used as a major proportion of the innerliners.

Accordingly, the air and moisture permeability resistance of the innerliner rubber composition is an important consideration.

The innerliner is normally prepared by conventional calendering or milling techniques to form a strip of uncured compounded rubber of appropriate width which is sometimes referred to as a gum strip. Typically, the gum strip is the first element of the tire applied to a tire building drum, over and around which the remainder of the tire is built. When the tire is cured, the innerliner becomes an integral, co-cured, part of the tire. Tire innerliners and their methods of preparation are well known to those having skill in such art.

There remains an ongoing desire to provide enhanced or suitable variations of butyl rubber-based tire innerliners without significantly affecting the air and moisture permeability resistance of the innerliner rubber composition.

In the description of the invention, the term “phr” relates to parts by weight of a particular ingredient per 100 parts by weight of rubber contained in a rubber composition. The terms “rubber” and “elastomer” are used interchangeably unless otherwise indicated, the terms “cure” and vulcanize” may be used interchangeably unless otherwise indicated and the terms “rubber composition” and “rubber compound” may be used interchangeably unless otherwise indicated. The term “butyl type rubber” is used herein to refer to butyl rubber (copolymer of isobutylene with a minor amount comprised of, for example about 1 to about 3 percent, of units derived from isoprene), and halobutyl rubber as chlorobutyl rubber and bromobutyl rubber (chlorinated and brominated butyl rubber, respectively) unless otherwise indicated. The term “partially depolymerized butyl rubber”, as used herein, is intended to be an ingredient other than an elastomer.

The term “Tm” relates to a melt point, or melting point, of a polymer, normally determined by a differential scanning calorimeter (DSC) with a temperature rise of from 3° C. to 10° C. per minute. The choice of temperature rise depends largely upon accuracy desired, with the 3° C. rise expected to be of greater accuracy, although a 10° C. temperature rise may often be used. The normal procedural aspect would be understood by one having skill in such art.

SUMMARY AND PRACTICE OF THE INVENTION

The present invention relates to a pneumatic rubber tire having an integral innerliner of a sulfur cured rubber composition. The innerliner is of a rubber composition comprised of, based upon parts by weight per 100 parts by weight of total rubber (phr),

(A) 100 phr of elastomers comprised of:

- (1) a butyl type rubber (not a partially depolymerized butyl type rubber) as:
  - (a) about 60 to 100, alternately about 60 to about 95, alternately about 60 to about 90 and alternately from about 60 to about 85, phr of halobutyl rubber selected from at least one of bromobutyl rubber and chlorobutyl rubber (halogenated butyl rubber) and their mixtures, and
  - (b) zero to about 30, alternately from about 5 to about 20, phr of butyl rubber (non-halogenated butyl rubber);
- (2) zero to about 40, and, depending upon the content, or level, of halogenated butyl rubber and of butyl rubber, if used, alternately from zero to about 30, zero to about 35, about 5 to about 30, about 5 to about 35, about 5 to about 40, phr of at least one diene-based elastomer selected from polymers of at least one of isoprene and 1,3-butadiene and copolymers of styrene and at least one of isoprene and 1,3-butadiene and their mixtures; preferably selected from styrene/butadiene copolymer, natural rubber and mixtures thereof, and
- (3) zero to about 30, alternately from about 5 to about 20, phr of at least one of partially depolymerized bromobutyl rubber, partially depolymerized chlorobutyl rubber, and partially depolymerized butyl rubber and their mixtures, and